GLAUCOMA AFTER PEDIATRIC PENETRATING KERATOPLASTY

DEFINITION
During the last academy meeting, the study group discussed the issue of glaucoma after pediatric penetrating keratoplasty. We were assisted in this by the presence of Dr. Jeffery Liebmann from The New York Eye & Ear Infirmary who, along with Dr. Robert Ritch, has managed a number of children with glaucoma following penetrating keratoplasty. Our first goal was to define glaucoma in these children. Dr. Liebmann pointed out that children can generally tolerate a higher intraocular pressure than adults. He feels that the intraocular pressure in children has to be consistently greater than 25mm Hg before there was any glaucomatous; damage. He would not diagnose glaucoma until there was documented progressive optic nerve cupping. This might not occur until the pressure was significantly greater than 25mm Hg. Therefore, elevation of the intraocular pressure is not sufficient to diagnose glaucoma and does not require treatment until nerve changes are noted. An IOP consistently greater than 30mm usually will require therapy.

DIAGNOSIS
Glaucoma can be checked with several methods though the preferred methods by Dr. Liebmann and the members of the study group appear to be the pneumotometer, the Perkins hand-held applanation tonometer or the tonopen. Palpation is also an effective method in some patients. Dr. Liebmann emphasized that the intraocular pressure has the tendency to fluctuate during an exam under anesthesia. He also prefers that inhalation anesthetics not be used since it can affect the intraocular pressure. He prefers that the child be anesthetized with ketamine and the IOP checked 5 minutes later. Chloral hydrate is an excellent way to check the intraocular pressure in the office.

INCIDENCE
The consensus of the group was that once patients with congenital glaucoma are eliminated, glaucoma probably occurs in about one third of the patients with congenital corneal opacities. Most discussants did not believe glaucoma was present in 50-60% of the patients as has been reported in some articles in the literature.

TREATMENT
If there is a normal cup to disc ratio, then treatment is necessary only to protect the corneal graft. If the graft is tolerating the pressure and the cup to disc ratio does not change, treatment is not needed. If the cup to disc ratio. begins to increase, then the pressure must be lowered. The initial treatment should be Betaxolol or carbonic anhydrase inhibitors. Timolol may rarely cause apnea. A few months after the keratoplasty, pilocarpine and other miotics can be tried.

If medical therapy fails, surgical therapy should first consist of a trabeculotomy. The next choice would be a mitomycin filtering procedure followed by cyclo destructive surgery using the YAG laser. Implant surgery can be considered but the long term risks, including graft failure and eventual loss of IOP control, are significant.

Because of the controversial nature of some of these conclusions, we hope to convene a round table discussions of these issues at the next PKA study group meeting (Academy, 1995). We plan for the round table to consist of several glaucoma specialists with expertise in this area.

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MANAGEMENT OF CHILD WITH CORNEAL DERMOID

There was general consensus on the management of the 9 day old patient with a corneal dermoid presented in the last newsletter. All the respondents said that their first step would be dilation (atropinization) of the pupil. This would be done along with periodic patching of the normal eye. Management of the patient would occur with the assistance of a pediatric ophthalmologist. If the child maintained equal and good fixation then this approach would be continued. However, if there was a demonstrable decrease in vision in the eye with the dermoid (by decreased fixation or any signs of strabismus), surgery would be indicated.

Most of the respondents would plan a lamellar keratectomy as their initial surgical approach. This would be done with donor tissue standing by in case the dermoid penetrated deeply into the posterior cornea or anterior chamber. There were two references given to support this approach (Vrabec, et al., Ophthalmic Surgery, June, 1994 and Zaidman, et al, American Journal of Ophthalmology, January, 1982). The respondents indicated that they would convert the lamellar keratectomy into a penetrating keratoplasty at the time of surgery if necessary. Another intriguing approach was a rotational autograft. Dr. Surendka Basti, Prasad Eye Institute, India, suggested that it might be possible to do a rotational autograft of approximately 8.25mm. This would assume an 11mm corneal diameter and that the dermoid encroached 5.5mm onto the cornea and 1mm beyond the limbus.

The clinical course of this child was as follows. The child was initially treated with part-time patching of the good eye and dilation of the affected eye. When the child was approximately three months of age, the pediatric ophthalmologist noticed decreased vision in the affected eye. Therefore, surgery was scheduled. The surgical plan was to be a lamellar dissection of the corneal dermoid.

The dermoid was not totally adherent to the cornea and could be lifted at the limbus. In this way a plane was dissected between the dermoid and the cornea. The dermoid was cut off of the central cornea and allowed to retract back to the limbus. A portion of the dermoid was excised. The dermoid had an oblique penetration into the corneal stroma such that the posterior cornea was more vascularized and opaque than the central anterior stroma. Therefore a penetrating keratoplasty of 6.5mm was necessary to create a clear visual axis. A Flieringa ring was placed. A 7.0mm. donor button was prepared. After the host cornea was excised, the donor button was sutured into place with 18 interrupted sutures of 10-0 prolene. Each suture bite was long enough to grab the limbus.

Post-operatively, the child was examined daily for three weeks with exams under anesthesia every 7-10 days until all sutures were removed. (Several of the interrupted sutures were removed on each exam.) All sutures were out by four weeks after surgery. The child was treated with prednisolone acetate and ciprofloxacin. Topical corticosteroids were initially used every hour and were tapered very slowly.

The child is now 12 months after surgery. He has maintained a clear corneal graft and has excellent and equal fixation in the affected eye. He is still on prednisolone acetate every other day.

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An 11 day old presented with bilateral congenital corneal opacities. The patient,-, systemic physical exam was normal. An examination under anesthesia of the right eye demonstrated sclerocornea. The left eye demonstrated lagophthalmos and an ectopic megalocornea (Figure 1). The corneal diameter appeared to be 12mm. The intraocular pressure could not he reliably checked. Transillumination demonstrated some pigment on the posterior aspect of the cornea. The axial length was 18mm. B-scan ultrasonography showed a possible pupillary membrane with a flat retina. A CT scan was obtained. The right eye was normal. The left eye showed a distended cornea, enlarged anterior segment, temporal displacement of a small lens and a possible pupillary membrane (arrow, Figure 2).

Corneal transplant surgery was performed at four weeks of age using a 12mm donor into an 11mm bed. At the time of surgery, pigment was present on the back of the endothelium with synechiae from the iris to the cornea and from the lens to the cornea.

The lens was shrunken, cataracts and displaced temporally. The vitreous face was covered with a pigmented membrane. No true iris or pupil was seen. These findings correlated with the findings on the CT scan.

We know that evaluation of the anterior segment in infants with opaque congenital corneal opacities is difficult. Poor patient cooperation usually requires an exam under anesthesia to elucidate the clinical findings. Modalities that have been used to "visualize" the anterior segment include transillumination and Aand B-scan ultrasonography. Recently, ultrabiomicroscopy has been shown to be of some benefit (Milner, Liebmann, et al., Ophthalmic Surgery, May, 1994). Most ophthalmologists do not have access or experience with this newly developed and expensive instrument. Judging from this case, it appears that CT scan may be of assistance in the diagnosis of these patients. Therefore, it may be helpful to obtain a CT scan on patients with these types of opaque congenital corneal opacities.

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